This invention relates to the surface treatment of so-called 312 ternary ceramic materials to provide increased surface hardness and to the surface-treated products so made.
A ternary titanium silicon carbide compound, having the formula Ti.sub.3 SiC.sub.2 and referred to as a 312 compound because of its 3-1-2 stoichiometry (and sometimes called titanium carbosilicide), has been the subject of recent research investigations reported in the literature. Most of these reports have been directed to Ti.sub.3 SiC.sub.2 synthesis methods and to characterization of its properties; see, e.g., Barsoum et al., J. Am. Ceram. Soc. 79: 1953-1956 (1996); Radhakrishnan et al., Scripta Materialia 34: 1809-1814 (1996); Arunajatesan et al., J. Am. Ceram. Soc. 78: 667-672 (1995); Lis et al., Materials Lett. 22: 163-168 (1995); Tong et al., J. Mater. Sci. 30: 3087-3090 (1995); Komarenko et al., Ceram. Eng. Sci Proc. 15: 1028-1035 (1994); Okano et al., Advanced Materials '93, I, A., "Ceramics, Powders, Corrosion and Advanced Processing", Mizutani, ed., Elsevier Science B.V., Amsterdam, pp. 597-600 (1994); Racault et al., J. Mater. Sci. 29: 3384-3392 (1994); Pampuch et al., J. Mater. Syn. Proc. 1:93-100(1993); and Pampuchet al., J. Europ. Ceram. Soc. 5:283-287 (1989).
Several reports describe use of or formation of Ti.sub.3 SiC.sub.2 as a bonding agent for joining silicon carbide workpieces; see, e.g., Morozumi et al., J. Mater. Sci. 20: 3976-3982 (1985) and Gottselig et al., U.S. Pat. No. 4,961,529.
The physical characteristics described for this relatively new ceramic material suggest that Ti.sub.3 SiC.sub.2 may be a ceramic material with unusual properties superior to those of conventional brittle ceramic materials. Ti.sub.3 SiC.sub.2 is a high strength, high temperature-stable material that has been characterized as having good workability, i.e., being ductile and exhibiting plastic behavior at elevated temperatures.
Methods for the synthesis of 312 ceramic compounds are described in pending U.S. patent application Ser. No. 08/726,473 of Barsoum et al., filed Mar. 6, 1996 and entitled "Synthesis of 312 Phases and Composites Thereof". A process for the densification of Ti.sub.3 SiC.sub.2 and other 312 ternary compounds is described in pending U.S. patent application Ser. No. 08/755,277 of Barsoum et al., filed Nov. 22, 1996 and entitled "Process for Making a Dense Ceramic Workpiece".
The physical characteristics and workability properties of these 312 ternary compounds make them useful as ceramics intended for high strength and high temperature applications.
The present invention provides a method for surface treating 312 ternary ceramic materials to provide improved physical properties for these materials.